If you know that you need more interaction than your friend, you may come off clingy to them. However, if you were friends with someone else, your need to be together may suit them just fine.
In short, you don't need to apologize for "being clingy," especially with a friend you have known a long time. Clingy behavior may be temporary, especially if you have been under stress, had your best friend move away, or had a major life change. In this case, your friend should be able to understand your need for togetherness and help you through it.
If your friendship is new, however, and you immediately want to be with your pal 24/7, it could mean that there are other issues in your life. Healthy friendships are not threatened when one person has other friends, so if you are feeling constantly left out or that your friends don't give you the time you need, ask yourself:
- Is this person perhaps not really as good a friend as I imagine?
- Is our friendship one-sided, with me doing most of the nurturing?
- Do I have codependent issues I need to work through?
If you answered yes to these questions, then you need to get to a healthy emotional place before you can have a balanced friendship. Rather than apologizing for "being clingy," you simply need to give your friend the space they require, develop more friendships of your own, and work through any personal issues.